IOS Surface shader transparency fix

Unity Engine
1

I just found on the net a shader that fits my needs.
My problem is that the shader does not have transparency on IOS and Graphics emulation.
Is there a limitation on IOS that busts the shader or what is going wrong with the shader?

Shader "Custom/VideoAlpha" {
       Properties {
          _MainTex ("Base (RGB)", 2D) = "white" {}
          _AlphaOffsetX ("alpha offset x", float) = 0.5
          _AlphaOffsetY ("alpha offset y", float) = 0
          _Cutoff ("Cutoff", Range (0,1)) = .5
       }
       SubShader {
       Tags {"Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Transparent"}
       LOD 300
       AlphaTest Less [_Cutoff]
             CGPROGRAM
            #pragma surface surf Lambert
       
             sampler2D _MainTex;
             float _AlphaOffsetX;
             float _AlphaOffsetY;
       
             struct Input {
                float2 uv_MainTex;
             };
       
             void surf (Input IN, inout SurfaceOutput o) {
                half4 c = tex2D (_MainTex, IN.uv_MainTex);
                IN.uv_MainTex.x += _AlphaOffsetX;
                IN.uv_MainTex.y += _AlphaOffsetY;
                half4 d = tex2D (_MainTex, IN.uv_MainTex);
                o.Albedo = c.rgb;
                o.Alpha = (d.r*-1)+1;
             }
             ENDCG
         
       }
       FallBack "Diffuse"
    }
2

Just found out that the shader just breaks and does FallBack to Diffuse.
Question remains, Why does the shader break?

Edit: Now its working … Some mysterious error and a wrong alpha channel was the Problem.